U.S. patent application number 14/812735 was filed with the patent office on 2016-02-25 for display device.
This patent application is currently assigned to OMRON Corporation. The applicant listed for this patent is OMRON Corporation. Invention is credited to Junya Fujita, Masaaki Hiramatsu, Takamitsu Ishikawa, Takeshi Kakinuma, Norihisa Kanzaki, Jun Kishimoto, Norikazu Kitamura, Yoshimasa Osumi, Masayuki Shinohara, Yoshihiko Takagi, Yasuhiro Tanoue.
Application Number | 20160054601 14/812735 |
Document ID | / |
Family ID | 55348211 |
Filed Date | 2016-02-25 |
United States Patent
Application |
20160054601 |
Kind Code |
A1 |
Kitamura; Norikazu ; et
al. |
February 25, 2016 |
DISPLAY DEVICE
Abstract
A display device has a liquid crystal panel that switches
between a transparent state and an opaque state, a first light
source, a light guide plate arranged on a back surface of the
liquid crystal panel and made of a transparent material, the light
guide plate having an incident surface facing the first light
source and an outgoing surface facing the back surface of the
liquid crystal panel, propagating light emitted from the first
light source and incident through the incident surface, and
outputting the light toward the liquid crystal panel from the
outgoing surface, and a second light source configured to
illuminate an object arranged on an opposite side to the liquid
crystal panel with the light guide plate interposed
therebetween.
Inventors: |
Kitamura; Norikazu; (Osaka,
JP) ; Osumi; Yoshimasa; (Kyoto, JP) ; Tanoue;
Yasuhiro; (Shiga, JP) ; Takagi; Yoshihiko;
(Kyoto, JP) ; Kanzaki; Norihisa; (Shiga, JP)
; Shinohara; Masayuki; (Kyoto, JP) ; Fujita;
Junya; (Aichi, JP) ; Ishikawa; Takamitsu;
(Aichi, JP) ; Kakinuma; Takeshi; (Gifu, JP)
; Kishimoto; Jun; (Gifu, JP) ; Hiramatsu;
Masaaki; (Aichi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OMRON Corporation |
Kyoto |
|
JP |
|
|
Assignee: |
OMRON Corporation
Kyoto
JP
|
Family ID: |
55348211 |
Appl. No.: |
14/812735 |
Filed: |
July 29, 2015 |
Current U.S.
Class: |
349/33 |
Current CPC
Class: |
G02B 6/0036 20130101;
G02B 6/0016 20130101 |
International
Class: |
G02F 1/137 20060101
G02F001/137; G02F 1/1335 20060101 G02F001/1335; F21V 8/00 20060101
F21V008/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 25, 2014 |
JP |
2014-170916 |
Claims
1. A display device comprising: a liquid crystal panel that
switches between a transparent state and an opaque state; a first
light source; a light guide plate arranged on a back surface of the
liquid crystal panel and made of a transparent material, the light
guide plate comprising an incident surface facing the first light
source and an outgoing surface facing the back surface of the
liquid crystal panel, propagating light emitted from the first
light source and incident through the incident surface, and
outputting the light toward the liquid crystal panel from the
outgoing surface; a second light source configured to illuminate an
object arranged on an opposite side to the liquid crystal panel
with the light guide plate interposed therebetween; and a
controller configured to put the liquid crystal panel into the
opaque state when the first light source is lit, to put the liquid
crystal panel into the transparent state when the second light
source is turned off while the second light source is lit, and to
turn off the first light source.
2. The display device according to claim 1, wherein a plurality of
patterns are formed in at least one of the outgoing surface of the
light guide plate and a surface on opposite side to the outgoing
surface, and wherein the plurality of patterns is formed into a
shape that reflects or refracts the light propagating through the
light guide plate such that the light output from the outgoing
surface, and an area ratio of a region where the plurality of
patterns are formed to the surface in which the plurality of
patterns are formed is less than or equal to 30%.
3. The display device according to claim 2, wherein the plurality
of patterns are arrayed at predetermined intervals along a
propagation direction of the light from the first light source in
the surface on the opposite side to the outgoing surface, and
wherein each of the plurality of patterns comprises a reflecting
surface that is inclined with respect to the surface on the
opposite side to the outgoing surface by an angle at which the
light, which is emitted from the first light source and incident on
the light guide plate from the incident surface, is totally
reflected toward the outgoing surface.
4. The display device according to claim 3, wherein the light guide
plate comprises a second incident surface that is formed so as to
face the incident surface with the plurality of patterns interposed
therebetween, wherein the first light source comprises a first
light emitting element that is arranged so as to face the incident
surface and a second light emitting element that is arranged so as
to face the second incident surface, and wherein each of the
plurality of patterns further comprises a second reflecting surface
that is inclined with respect to the surface on the opposite side
to the outgoing surface by an angle at which the light, which is
emitted from the second light emitting element and incident on the
light guide plate from the second incident surface, is totally
reflected toward the outgoing surface.
5. The display device according to claim 1, wherein a haze value of
the light guide plate to the light, which is incident on the light
guide plate from the surface on the opposite side to the outgoing
surface and transmitted onto the outgoing surface side, is less
than or equal to 28%.
6. The display device according to claim 1, further comprising: a
direction-selective light shielding member formed into a sheet
shape between the light guide plate and the object, wherein the
direction-selective light shielding member comprises a first
surface facing the light guide plate and a second surface facing
the object, wherein the direction-selective light shielding member
comprises, inside thereof, a plurality of opaque members arranged
at predetermined intervals along the propagation direction of the
light from the first light source, and wherein the plurality of
opaque members being extended in a direction intersecting the
propagation direction.
7. The display device according to claim 2, wherein a haze value of
the light guide plate to the light, which is incident on the light
guide plate from the surface on the opposite side to the outgoing
surface and transmitted onto the outgoing surface side, is less
than or equal to 28%.
8. The display device according to claim 3, wherein a haze value of
the light guide plate to the light, which is incident on the light
guide plate from the surface on the opposite side to the outgoing
surface and transmitted onto the outgoing surface side, is less
than or equal to 28%.
9. The display device according to claim 4, wherein a haze value of
the light guide plate to the light, which is incident on the light
guide plate from the surface on the opposite side to the outgoing
surface and transmitted onto the outgoing surface side, is less
than or equal to 28%.
10. The display device according to claim 2, further comprising: a
direction-selective light shielding member formed into a sheet
shape between the light guide plate and the object, wherein the
direction-selective light shielding member comprises a first
surface facing the light guide plate and a second surface facing
the object, wherein the direction-selective light shielding member
comprises, inside thereof, a plurality of opaque members arranged
at predetermined intervals along the propagation direction of the
light from the first light source, and wherein the plurality of
opaque members being extended in a direction intersecting the
propagation direction.
11. The display device according to claim 3, further comprising: a
direction-selective light shielding member formed into a sheet
shape between the light guide plate and the object, wherein the
direction-selective light shielding member comprises a first
surface facing the light guide plate and a second surface facing
the object, wherein the direction-selective light shielding member
comprises, inside thereof, a plurality of opaque members arranged
at predetermined intervals along the propagation direction of the
light from the first light source, and wherein the plurality of
opaque members being extended in a direction intersecting the
propagation direction.
12. The display device according to claim 4, further comprising: a
direction-selective light shielding member formed into a sheet
shape between the light guide plate and the object, wherein the
direction-selective light shielding member comprises a first
surface facing the light guide plate and a second surface facing
the object, wherein the direction-selective light shielding member
comprises, inside thereof, a plurality of opaque members arranged
at predetermined intervals along the propagation direction of the
light from the first light source, and wherein the plurality of
opaque members being extended in a direction intersecting the
propagation direction.
13. The display device according to claim 5, further comprising: a
direction-selective light shielding member formed into a sheet
shape between the light guide plate and the object, wherein the
direction-selective light shielding member comprises a first
surface facing the light guide plate and a second surface facing
the object, wherein the direction-selective light shielding member
comprises, inside thereof, a plurality of opaque members arranged
at predetermined intervals along the propagation direction of the
light from the first light source, and wherein the plurality of
opaque members being extended in a direction intersecting the
propagation direction.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to Japanese Patent
Application No. 2014-170916 filed with the Japan Patent Office on
Aug. 25, 2014, the entire contents of which are incorporated herein
by reference.
BACKGROUND
[0002] 1. Field
[0003] The present invention relates to a display device that can
switch between a transparent state and an opaque state.
[0004] 2. Related Art
[0005] Conventionally, there is proposed an element having a light
control function of transmitting light in the transparent state and
of shielding the light in the opaque state (for example, see
Unexamined Japanese Patent Publication No. 2013-28082).
[0006] For example, a light control film disclosed in Unexamined
Japanese Patent Publication No. 2013-28082 includes: two
transparent conductive resin base materials; a light control layer
that is sandwiched between the two base materials to include a
resin matrix and a light controlling suspension dispersed in the
resin matrix; and a primer layer that is provided between the
transparent conductive resin base material and the light control
layer, the primer layer containing an organic binder resin and
silicon dioxide particles, an average film thickness of the primer
layer ranging from 30 nm to 75 nm.
[0007] The light control film maintains a clear coloring state
without light scattering unless an electric field is applied, and
the light control film is converted into the transparent state when
the electric field is applied.
SUMMARY
[0008] However, in the light control film disclosed in Unexamined
Japanese Patent Publication No. 2013-28082, a response time ranges
from 1 second to 50 seconds with respect to the electric field
during a decoloring state, the response time ranges from 1 second
to 100 seconds with respect to the electric field during the
coloring state, and the response time is too long. For this reason,
the light control film is not suitable for applications in which
switching between the transparent state and the opaque state is
required in a short time.
[0009] One or more embodiments of the present invention provides a
display device that can enhance the response speed of the switching
between the transparent state and the opaque state.
[0010] A display device according to one or more embodiments of the
present invention comprises a liquid crystal panel configured to be
able to switch between a transparent state and an opaque state; a
first light source; a light guide plate arranged on a back surface
of the liquid crystal panel and made of a transparent material, the
light guide plate including an incident surface facing the first
light source and an outgoing surface facing the back surface of the
liquid crystal panel, in which the light guide plate propagates
light inside thereof, the light being emitted from the first light
source and incident through the incident surface, and outputs the
light toward the liquid crystal panel from the outgoing surface; a
second light source configured to illuminate an object arranged on
an opposite side to the liquid crystal panel with the light guide
plate interposed therebetween; and a controller configured to put
the liquid crystal panel into the opaque state when the first light
source is lit, to put the liquid crystal panel into the transparent
state when the second light source is turned off while the second
light source is lit, and to turn off the first light source.
[0011] In the display device, according to one or more embodiments
of the present invention, a plurality of patterns are formed in at
least one of the outgoing surface of the light guide plate and a
surface on opposite side to the outgoing surface, the plurality of
patterns being formed into a shape that reflects or refracts the
light propagating through the light guide plate such that the light
output from the outgoing surface, and an area ratio of a region
where the plurality of patterns are formed to the surface in which
the plurality of patterns are formed is less than or equal to
30%.
[0012] In the display device, according to one or more embodiments
of the present invention, the plurality of patterns are arrayed at
predetermined intervals along a propagation direction of the light
from the first light source in the surface on the opposite side to
the outgoing surface, and each of the plurality of patterns
includes a reflecting surface that is inclined with respect to the
surface on the opposite side to the outgoing surface by an angle at
which the light, which is emitted from the first light source and
incident on the light guide plate from the incident surface, is
totally reflected toward the outgoing surface.
[0013] According to one or more embodiments of the present
invention, the light guide plate includes a second incident surface
that is formed so as to face the incident surface with the
plurality of patterns interposed therebetween. According to one or
more embodiments of the present invention, the first light source
includes a first light emitting element that is arranged so as to
face the incident surface and a second light emitting element that
is arranged so as to face the second incident surface. According to
one or more embodiments of the present invention, each of the
plurality of patterns further includes a second reflecting surface
that is inclined with respect to the surface on the opposite side
to the outgoing surface by an angle at which the light, which is
emitted from the second light emitting element and incident on the
light guide plate from the second incident surface, is totally
reflected toward the outgoing surface.
[0014] In the display device, according to one or more embodiments
of the present invention, a haze value of the light guide plate to
the light, which is incident on the light guide plate from the
surface on the opposite side to the outgoing surface and
transmitted onto the outgoing surface side, is less than or equal
to 28%.
[0015] According to one or more embodiments of the present
invention, the display device further includes a
direction-selective light shielding member formed into a sheet
shape between the light guide plate and the object, the
direction-selective light shielding member including a first
surface facing the light guide plate and a second surface facing
the object, the direction-selective light shielding member
including inside thereof a plurality of opaque members arranged at
predetermined intervals along the propagation direction of the
light from the first light source, the plurality of opaque members
being extended in a direction intersecting the propagation
direction.
[0016] The display device according to one or more embodiments of
the present invention may be able to enhance the response speed of
the switching between the transparent state and the opaque
state.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic configuration diagram illustrating a
display device according to one or more embodiments of the present
invention;
[0018] FIG. 2A is a schematic front view illustrating the display
device when a liquid crystal panel is in an opaque state, and FIG.
2B is a schematic front view illustrating the display device when
the liquid crystal panel is in a transparent state;
[0019] FIG. 3A is a sectional side view illustrating a light guide
plate; FIG. 3B is a sectional side view illustrating the light
guide plate on which light are incident from two directions;
[0020] FIG. 4A is a partially enlarged sectional side view
illustrating a shape of a reflecting surface of a prism in a light
guide plate according to a modification, and FIG. 4B is a partially
enlarged sectional side view illustrating a shape of a reflecting
surface of a prism in a light guide plate according to another
modification;
[0021] FIG. 5 is a view illustrating a table expressing a
relationship among a pattern density, a haze value, and a
visibility of the object 10 viewed by the observer;
[0022] FIGS. 6A to 6C are views illustrating examples of an
arrangement pattern of the prism when the pattern density is less
than or equal to 30.0% and when the haze value is less than or
equal to 28%;
[0023] FIG. 7 is a sectional side view illustrating a light guide
plate according to a modification;
[0024] FIG. 8 is a sectional side view illustrating a light guide
plate according to another modification;
[0025] FIG. 9 is a sectional side view illustrating a light guide
plate according to still another modification;
[0026] FIG. 10 is a schematic configuration diagram illustrating a
display device according to a modification including a louver film;
and
[0027] FIG. 11 is a schematic perspective view illustrating a
pachinko game machine including the display device of the
embodiment and the modifications when the pachinko game machine is
viewed from a player side.
DETAILED DESCRIPTION
[0028] Hereinafter, embodiments of the present invention will be
described with reference to the drawings. In embodiments of the
invention, numerous specific details are set forth in order to
provide a more thorough understanding of the invention. However, it
will be apparent to one of ordinary skill in the art that the
invention may be practiced without these specific details. In other
instances, well-known features have not been described in detail to
avoid obscuring the invention.
[0029] A liquid crystal panel that can switch between a transparent
state and an opaque state is used in the display device, and
arranged between an object presented to an observer and the
observer. In the display device, while the liquid crystal panel is
in the opaque state, the liquid crystal panel is illuminated from a
back surface with light emitted from liquid crystal panel
illuminating light source arranged in a side surface of a light
guide plate through the light guide plate arranged on the back
surface of the liquid crystal panel to display an image or a
pattern on the liquid crystal panel, and an object illuminating
light source behind the liquid crystal panel is turned off, whereby
the observer is made blind to the object. On the other hand, in the
display device, the liquid crystal panel is put into the
transparent state, the liquid crystal panel illuminating light
source is turned off, and the object illuminating light source is
lit, whereby the observer can visually recognize the object through
the liquid crystal panel. Therefore, the display device can switch
between display and non-display of the object at a response speed
of the liquid crystal panel.
[0030] Hereinafter, for convenience of explanation, it is assumed
that the side facing the observer is a front surface while an
opposite side to the front surface is a back surface.
[0031] FIG. 1 is a schematic configuration diagram illustrating the
display device according to one embodiment of the present
invention. A display device 1 includes a liquid crystal panel 2, a
light guide plate 3, a first light source 4, a second light source
5, and a controller 6.
[0032] The liquid crystal panel 2 is a panel configured to switch
between the transparent state and the opaque state according to a
voltage applied from the controller 6. For example, the liquid
crystal panel 2 includes a liquid crystal layer in which liquid
crystal molecules are sealed, two transparent electrodes, two
transparent substrates, and two polarizing plates. The transparent
electrodes made of ITO are arranged so as to face each other with
the liquid crystal layer interposed therebetween. The transparent
substrates made of glass or transparent resin are arranged so as to
face each other with the liquid crystal layer and the transparent
electrode interposed therebetween. The polarizing plates are
arranged so as to face each other with the liquid crystal layer,
the transparent electrode, and the transparent substrate interposed
therebetween. An oriented film may be formed between the liquid
crystal layer and the transparent electrode in order to define
orientations of the liquid crystal molecules. One of the
transparent electrodes may be formed in a matrix state so as to be
able to adjust a voltage applied in units of pixels.
[0033] For example, the two oriented films orient the liquid
crystal molecules of the liquid crystal layer toward a
predetermined direction. For example, in the case that the liquid
crystal molecules included in the liquid crystal layer are arrayed
into a twist nematic type, the two oriented films are arranged such
that the orientations of the oriented films are orthogonal to each
other. Each of the two polarizing plates is an element configured
to transmit a polarization component having a polarization plane in
a specific direction. For example, the two polarizing plates are
arranged such that transmission axes of the polarizing plates are
orthogonal to each other in order to cause the crystal panel 2 to
operate in a normally white mode. Unless an electric field is
applied between the two transparent electrodes between which the
liquid crystal layer is interposed, a polarization direction of the
light transmitted through the polarizing plate arranged on a back
surface side rotates in the liquid crystal layer by 90.degree..
Therefore, the light can be transmitted through the polarizing
plate arranged on a front surface side. Therefore, the liquid
crystal panel becomes transparent. On the other hand, when an
electric field is applied between the two transparent electrodes
between which the liquid crystal layer is interposed, the
polarization plane of the light transmitted through the liquid
crystal layer does not rotate because the liquid crystal molecules
in the liquid crystal layer are oriented toward a direction
parallel to the electric field. Therefore, the liquid crystal panel
becomes opaque because the light transmitted through the polarizing
plate arranged on the back surface side cannot be transmitted
through the polarizing plate arranged on the front surface
side.
[0034] The polarizing plates may be arranged such that transmission
axes of the polarizing plates are parallel to each other in order
to cause the crystal panel 2 to operate in a normally black mode.
The liquid crystal panel becomes transparent when the electric
field is applied between the two transparent electrodes between
which the liquid crystal layer is interposed, and the liquid
crystal panel becomes opaque unless the electric field is applied
between the two transparent electrodes between which the liquid
crystal layer is interposed.
[0035] The liquid crystal panel 2 is not limited to the above
liquid crystal panel, but any liquid crystal panel may be used as
long as the liquid crystal panel can switch between the transparent
state and the opaque state in response to a control signal from the
controller 6.
[0036] FIG. 2A is a schematic front view illustrating the display
device when the liquid crystal panel is in the opaque state, and
FIG. 2B is a schematic front view illustrating the display device
when the liquid crystal panel is in the transparent state. As
illustrated in FIG. 2A, when the liquid crystal panel 2 is in the
opaque state, an object 10 behind thereof hides behind a display
region of the liquid crystal panel 2, and the observer cannot
visually recognize the object 10. On the other hand, as illustrated
in FIG. 2B, when the liquid crystal panel 2 is in the transparent
state, the observer can visually recognize the object 10 through
the display region of the liquid crystal panel 2.
[0037] When the first light source 4 is lit, the light emitted from
the first light source 4 is diffusely propagated through the light
guide plate 3, and output toward the liquid crystal panel 2,
thereby illuminating the liquid crystal panel 2 with the light.
When the second light source 5 is lit, the light from the object 10
illuminated by the second light source 5 is transmitted through the
light guide plate 3 from the back surface side to the side of the
liquid crystal panel 2. Therefore, the light guide plate 3 is a
sheet-like member having an area larger than an active region where
the liquid crystal molecules of the liquid crystal panel 2 can be
driven, and the light guide plate 3 is arranged so as to face the
back surface of the liquid crystal panel 2. For example, the light
guide plate 3 is formed by molding resins, such as
polymethylmethacrylate (PMMA), polycarbonate, and cycloolefin
polymer, which are transparent to visible light.
[0038] An incident surface 3a is formed in one of side surfaces of
the light guide plate 3 so as to face the first light source 4, and
the light emitted from the first light source 4 is incident on the
light guide plate 3 from the incident surface 3a. The light
propagated through the light guide plate 3 is totally reflected by
a diffusing surface 3b located on the back surface side, output
from an outgoing surface 3c facing the back surface of the liquid
crystal panel 2, and incident on the liquid crystal panel 2.
[0039] When the second light source 5 is lit, the light emitted
from the second light source 5 is reflected or diffused by the
object 10, then incident on the light guide plate 3 from the
diffusing surface 3b of the light guide plate 3, transmitted
directly through the light guide plate 3, and output toward the
liquid crystal panel 2 from the outgoing surface 3c.
[0040] FIG. 3A is a sectional side view illustrating the light
guide plate 3 along a propagation direction of the light
perpendicularly incident on the incident surface of the light guide
plate from the first light source 4. In the embodiment, the
incident surface 3a is formed so as to be orthogonal to the
diffusing surface 3b and the outgoing surface 3c. The incident
surface 3a may be formed into a shape convex toward the first light
source 4 so as to act as a collimate lens that enhances
directionality of the light incident from the first light source
4.
[0041] A plurality of prisms 11 are formed in the diffusing surface
3b so as to reflect the light incident from the incident surface
3a, to uniformly output the light from the whole outgoing surface
3c, and to cause the light to be incident substantially
perpendicularly on the liquid crystal panel 2.
[0042] The plurality of prisms 11 are arrayed with a predetermined
pitch along the propagation direction of the incident light
incident from the incident surface 3a. In the diffusing surface 3b,
each prism 11 is formed as a substantially triangular groove that
is extended in a direction substantially perpendicular to the
propagation direction of the incident light incident from the
incident surface 3a. Each prism 11 includes a reflecting surface 12
that forms a predetermined angle with respect to the diffusing
surface 3b. The predetermined angle is fixed according to the
propagation direction of the incident light and the direction of
the light output from the light guide plate 3. In the embodiment,
the propagation direction of the incident light is substantially
parallel to the diffusing surface 3b, and the light guide plate 3
outputs the light in the direction substantially perpendicular to
the outgoing surface 3c. Therefore, for example, each reflecting
surface 12 is formed so as to form an angle of 37.degree. to
45.degree. with respect to the diffusing surface 3b. Particularly,
each reflecting surface 12 is desirably provided such that an angle
.alpha. (unit: .degree.) formed between the reflecting surface 12
and the diffusing surface 3b satisfies the following condition.
.alpha.<90-tan-1(sqrt(n2-1)) (1)
where n is a refractive index of the light guide plate 3.
Additionally, the light emitting element included in the first
light source 4 is desirably selected such that a half-value angle
.beta. (unit: .degree.) of the light emitted from the first light
source 4 satisfies the following condition.
.beta.<109.74n-155.06 (2)
[0043] For example, in the case that the light guide plate 3 is
made of PMMA (refractive index n=1.49), .alpha.<42.17.degree.
and .beta.<8.5.degree. are obtained. In the case that the light
guide plate 3 is made of polycarbonate (refractive index n=1.59),
.alpha.<38.97.degree. and .beta.<19.4.degree. are
obtained.
[0044] In this case, because the incident angle of the light
incident on each reflecting surface 12 is larger than a critical
angle, the incident light is totally reflected by each reflecting
surface 12 as indicated by an arrow 301. Therefore, the light guide
plate 3 restrains the incident light of the first light source 4
from outputting from the side of the diffusing surface 3b, which
allows restraint of a light quantity that is not used in the
illumination of the liquid crystal panel 2.
[0045] In the case that the liquid crystal panel 2 is in the opaque
state when the observer obliquely views the display device 1,
desirably a viewing angle is ensured to a certain extent such that
an image displayed on the liquid crystal panel 2 is viewed. For
example, in order to ensure the viewing angle of 15.degree. or
more, desirably the angle .alpha. formed between the reflecting
surface 12 and the diffusing surface 3b and the half-value angle
.beta. of the first light source 4 satisfy the following
conditions.
.alpha.<1.4924n+40.274 (3)
.beta.<-0.0327n+7.5127 (4)
[0046] For example, in the case that the light guide plate 3 is
made of PMMA (refractive index n=1.49), .alpha.<42.5.degree. and
.beta.<7.46.degree. are obtained. In the case that the light
guide plate 3 is made of polycarbonate (refractive index n=1.59),
.alpha.<42.7.degree. and .beta.<7.46.degree. are
obtained.
[0047] Desirably the pitch between adjacent prisms 11 is kept
constant such that the intensity of the light output from the
outgoing surface 3c is uniformed regardless of the position.
[0048] As illustrated in FIG. 3B, two incident surfaces 3a and 3d
may be formed in two side surfaces facing each other in the light
guide plate 3 so as to face each other with the plurality of prisms
11 interposed therebetween. The first light source 4 may include a
light emitting element that emits the light incident on the light
guide plate 3 from the incident surface 3a and a light emitting
element that emits the light incident on the light guide plate 3
from the incident surface 3d. In this case, both the surfaces of
each prism 11 constitute the reflecting surface 12 that is formed
so as to satisfy the expression (1) or (3) with respect to the
diffusing surface 3b, and the surfaces totally reflect the incident
light toward the side of the outgoing surface 3c. For example, a
light emitting element having the half-value angle satisfying the
expression (2) or (4) is used as the light emitting element that is
arranged so as to face the incident surface 3d.
[0049] In this modification, a range (a range surrounded by arrows
311 and 312) where the light, which is incident from the side of
the incident surface 3a and output from the outgoing surface 3c,
spreads and a range (a range surrounded by arrows 313 and 314)
where the light, which is incident from the side of the incident
surface 3d and output from the outgoing surface 3c, spreads are
opposite to each other with respect to a normal n of the outgoing
surface 3c. Therefore, the viewing angle becomes wider than the
example in FIG. 3A.
[0050] In another modification, the side surface facing the
incident surface 3a of the light guide plate 3 may be formed into a
mirror surface such that the light propagating through the light
guide plate 3 is reflected toward the inside of the light guide
plate 3. In this case also, the effect similar to that of the above
modification is obtained.
[0051] In still another modification, the incident surface 3a may
be formed so as to form an angle of 45.degree. with respect to the
diffusing surface 3b as indicated by a dotted line in FIG. 3A. In
this case also, for example, the light incident on the light guide
plate 3 from the incident surface 3a is incident on the diffusing
surface 3b and the outgoing surface 3c at the angle of about
45.degree., and totally reflected by the diffusing surface 3b and
the outgoing surface 3c, thereby propagating through the light
guide plate 3. In this case, for the light propagating through the
light guide plate 3 to reach the prism 11, sometimes the angle
incident on the reflecting surface 12 is less than the critical
angle. However, even in this case, as indicated by an arrow 302,
because the light is refracted toward the side of the diffusing
surface 3b when output from the reflecting surface 12, the light is
incident on the light guide plate 3 again from the surface farther
away from the light source 4 of the prism 11. Therefore, a loss of
the amount of light output onto the side of the back surface side
from the diffusing surface 3b is restrained.
[0052] In yet another modification, as illustrated in FIG. 4A, the
reflecting surface 12 of the prism 11 may be formed by a plurality
of flat surfaces 12a and 12b such that an inclination angle of the
reflecting surface 12 with respect to the diffusing surface 3b
increases toward the outgoing surface 3c. Alternatively, the
reflecting surface 12 may be formed into a cylindrical surface such
that the cylindrical surface is concave to the incident surface 3a,
and such that the center of the cylindrical surface is parallel to
the outgoing surface 3c. In this case, the directionality of the
light output from the outgoing surface 3c is enhanced.
Alternatively, as illustrated in FIG. 4B, the reflecting surface 12
of the prism 11 may be formed by a plurality of flat surfaces 12c
and 12d such that the reflecting surface 12 is convex to the
incident surface 3a, and such that an inclination angle of the
reflecting surface 12 with respect to the diffusing surface 3b
increases toward the outgoing surface 3c. Alternatively, the
reflecting surface 12 may be formed into a cylindrical surface such
that the cylindrical surface is convex to the incident surface 3a,
and such that the center of the cylindrical surface is parallel to
the outgoing surface 3c. In this case, because the light incident
on the light guide plate 3 is reflected by the reflecting surface
12 to spread, the viewing angle becomes wider.
[0053] Desirably the pattern density, which is a ratio of an area
of a region where the prism 11 is formed to an area of the
diffusing surface 3b, is less than or equal to an upper limit of
the pattern density at which the observer feels the visual
recognition of the object 10 behind the light guide plate 3 through
the transparent member or an empty space when the liquid crystal
panel 2 becomes the transparent state. On the other hand, desirably
the pattern density is greater than or equal to a lower limit of
the pattern density at which the observer can visually recognize
the image or pattern displayed on the liquid crystal panel 2 with
the light emitted from the first light source 4 when the liquid
crystal panel 2 becomes the opaque state.
[0054] Alternatively, desirably the haze value expressing a
percentage of the diffused light to the whole transmitted light is
less than or equal to the upper limit of the haze value at which
the observer feels the visual recognition of the object 10 behind
the light guide plate 3 through the transparent member or the empty
space when the liquid crystal panel 2 becomes the transparent
state.
[0055] FIG. 5 is a table illustrating a relationship among the
pattern density, a haze value, and a visibility of the object 10
viewed by the observer in a visual test. In a table 500, a left-end
column expresses the pattern density, a central column expresses
the haze value, and a right-end column expresses a visual
recognition result. In the visual test, one chip type white LED
(LP-3020H196W) was used as the second light source 5. The haze
value was measured with a haze meter HM-150L2 (product of MURAKAMI
COLOR RESEARCH LABORATORY CO., Ltd.). In visually observing the
object 10 illuminated by the second light source 5 through the
light guide plate 3 and the liquid crystal panel 2 in the
transparent state, the visual test is good (OK) when the observer
feels that the member in front of the object 10 is the transparent
member, and the visual test is bad (NG) when the observer feels
that the opaque member exists in front of the object 10.
[0056] As illustrated in the table 500, the visual recognition
result becomes NG when the pattern density is greater than 30% or
when the haze value is greater than 28%. Therefore, for example,
desirably each prism 11 is formed such that the pattern density is
less than or equal to 30.0%. Alternatively, desirably each prism 11
is formed such that the haze value is less than or equal to
28%.
[0057] FIGS. 6A to 6C are views illustrating examples of an
arrangement pattern of the prism when the pattern density is less
than or equal to 30.0% and when the haze value is less than or
equal to 28%. In the examples of FIGS. 6A to 6C, for each prism 11,
a length W along the propagation direction of the incident light is
27.5 .mu.m, and a length L in the direction orthogonal to the
propagation direction of the incident light is 55 .mu.m. For
example, in the case of the pattern density of about 30.0% and the
haze value of about 28%, the prisms 11 are arranged in a zigzag
manner with a pitch of 50 .mu.m like an arrangement pattern 601 in
FIG. 6A.
[0058] Alternatively, the prisms 11 may be arranged into a lattice
shape like an arrangement pattern 602 in FIG. 6B. In this case, for
example, the prisms 11 are arranged with a pitch of 100 .mu.m.
[0059] Alternatively, like an arrangement pattern 603 in FIG. 6C,
the prisms 11 may be arranged such that the number of prisms 11
varies in each column of the direction orthogonal to the incident
surface 3a.
[0060] For example, the first light source 4 includes a light
emitting element such as a white light emitting diode and a
fluorescent light, and is arranged such that an emission surface of
the first light source 4 faces the incident surface 3a of the light
guide plate 3. For example, the first light source 4 is arranged
such that the direction of the strongest emission intensity of the
first light source 4 is orthogonal to the incident surface 3b. For
example, desirably a light emitting element having the
directionality is used as the first light source 4 in order to
enhance use efficiency of the light. Alternatively, a collimate
lens may be arranged between the incident surface 3b and the first
light source 4 in order to enhance the directionality of the light
emitted from the first light source 4. The first light source 4 may
include a plurality of light emitting elements. The first light
source 4 is lit or turned off in response to the control signal
from the controller 6.
[0061] For example, the second light source 5 includes a light
emitting element such as a white light emitting diode and a
fluorescent light, and is arranged so as to illuminate the object
10 arranged on the back surface side of the light guide plate 3. In
order to illuminate the object 10 with the light source having a
specific color, a light emitting element, such as a diode, which
emits the light having the specific color may be used as the second
light source 5. In the case that the object 10 is opaque, desirably
the second light source 5 is arranged at the position closer to
light guide plate 3 than the object 10 such that the light
reflected or scattered by the object 10 is incident on the light
guide plate 3. The second light source 5 may include a plurality of
light emitting elements. For example, the second light source 5 may
include a plurality of light emitting elements that are arranged so
as to surround the object 10. The second light source 5 itself may
be an object that is observed through the display region of the
liquid crystal panel 2. Desirably the second light source 5 is
arranged such that the light from the second light source 5 is not
directly incident on the incident surface 3a of the light guide
plate 3. Similarly to the first light source 4, the second light
source 5 is lit or turned off in response to the control signal
from the controller 6.
[0062] For example, the controller 6 includes a processor, a memory
circuit, and a driving circuit of the liquid crystal panel 2. In
response to a control signal of a superior control device (not
illustrated), the controller 6 controls the liquid crystal panel 2,
the first light source 4, and the second light source 5. In order
to make the observer located on the front surface side of the
liquid crystal panel 2 blind to the object 10, the controller 6
puts the liquid crystal panel 2 into the opaque state. The
controller 6 lights the first light source 4 while turning off the
second light source 5. On the other hand, in order to make the
observer located on the front surface side of the liquid crystal
panel 2 see the object 10, the controller 6 puts the liquid crystal
panel 2 into the transparent state. The controller 6 turns off the
first light source 4 while lighting the second light source 5.
[0063] As described above, in the display device, the controller
switches between the transparent state and opaque state of the
liquid crystal panel, which enables or disables the object behind
the liquid crystal panel to be visually recognized by the observer.
Therefore, the display device can switch between display and
non-display of the object at a response speed of the liquid crystal
panel. The response speed of the liquid crystal panel is less than
100 milliseconds or 1 second, so that the display device can
enhance the response speed of the switching between the display and
the non-display. In the display device, both the liquid crystal
panel and the light guide plate does not have wavelength
selectivity too high, so that the object is not colored even if the
observer views the object through the liquid crystal panel and the
light guide plate.
[0064] In a modification, the pattern formed in the diffusing
surface 3b of the light guide plate 3 may be a trapezoidal pattern
that projects from the diffusing surface 3b toward the side of the
object 10.
[0065] FIG. 7 is a sectional side view illustrating the light guide
plate 3 of the modification. In the embodiment, the incident
surface 3a is formed so as to be orthogonal to the diffusing
surface 3b and the outgoing surface 3c. A plurality of trapezoidal
prisms 21 are formed in the diffusing surface 3b so as to reflect
the light incident from the incident surface 3a, to uniformly
output the light from the whole outgoing surface 3c, and to cause
the light to be incident substantially perpendicularly on the
liquid crystal panel 2.
[0066] The plurality of trapezoidal prisms 21 are arrayed with a
predetermined pitch along the propagation direction of the incident
light incident from the incident surface 3a. In the diffusing
surface 3b, each prism 21 is formed as a trapezoidal projection
along a direction substantially perpendicular to the propagation
direction of the incident light from the incident surface 3a.
Desirably, in the case that the light propagating through the light
guide plate 3 has a small angle with respect to the diffusing
surface 3b, a slope 22 of each prism 21 on the side farther away
from the light source 4 is formed so as to totally reflect the
light onto the side of the outgoing surface 3c as indicated by an
arrow 701. Desirably, even in the case that the light propagating
through the light guide plate 3 can hardly be totally reflected
because the light has a relatively large angle with respect to the
diffusing surface 3b, the slope 22 is formed such that the light
output to the outside of the light guide plate 3 from the slope 22
is refracted by the slope 22 toward the side of the diffusing
surface 3b as indicated by an arrow 702. For example, desirably the
slope 22 is formed so as to form the angle of 45.degree. with
respect to the diffusing surface 3b. There is no particular
limitation to the slope of each prism 21 on the side closer to the
light source 4, but the slope may have an angle at which the light
guide plate 3 is easily mold.
[0067] In this modification, desirably each prism 21 is formed such
that the pattern density is less than or equal to 30%, or such that
the haze value is less than or equal to 28%. For example, desirably
each prism 21 is formed such that the prism 21 has a width of 30
.mu.m along the propagation direction of the incident light, and
such that an interval between the two adjacent prisms 21 is 100
.mu.m.
[0068] In another modification, the diffusing surface 3b of the
light guide plate 3 may be formed on a flat surface so as to
totally reflect the light propagating through the light guide plate
3, and a plurality of trapezoidal prisms may be formed on the side
of the outgoing surface 3c.
[0069] FIG. 8 is a sectional side view illustrating the light guide
plate 3 of the modification. In the embodiment, for example, the
incident surface 3a is formed at the angle of 45.degree. with
respect to the diffusing surface 3b such that the light from the
first light source 4 propagates through the light guide plate 3 at
the angle at which almost the light is totally reflected by the
diffusing surface 3b. The first light source 4 is also arranged
such that the direction of the strongest emission intensity of the
first light source 4 is orthogonal to the incident surface 3a. In
this case, for example, the light incident on the light guide plate
3 from the incident surface 3a is incident on the diffusing surface
3b and the outgoing surface 3c at the angle of about 45.degree.,
and totally reflected by the diffusing surface 3b and the outgoing
surface 3c, thereby propagating through the light guide plate 3. A
plurality of trapezoidal prisms 31 are formed in the outgoing
surface 3c such that the incident light totally reflected by the
diffusing surface 3b is output onto the side of the liquid crystal
panel 2.
[0070] The plurality of trapezoidal prisms 31 are arrayed with a
predetermined pitch along the propagation direction of the incident
light incident from the incident surface 3a. In the outgoing
surface 3c, each prism 31 is formed as a trapezoidal projection
along a direction substantially perpendicular to the propagation
direction of the incident light from the incident surface 3a.
Desirably, a slope 32 of each prism 31 on the side farther away
from the light source 4 is formed such that the light propagating
through the light guide plate 3 is refracted by the slope 32 and
oriented toward the direction substantially orthogonal to the
outgoing surface 3c as indicated by an arrow 801. For example,
desirably the slope 32 is formed so as to form an angle of
70.degree. to 80.degree. with respect to the outgoing surface 3c.
There is no particular limitation to the slope of each prism 31 on
the side closer to the light source 4, but the slope may have an
angle at which the light guide plate 3 is easily mold.
[0071] Even in this modification, desirably each prism 31 is formed
such that the pattern density is less than or equal to 30%, or such
that the haze value is less than or equal to 28%. For example,
desirably each prism 31 is formed such that the prism 31 has a
width of 30 .mu.m along the propagation direction of the incident
light, and such that an interval between the two adjacent prisms 31
is 100 .mu.m.
[0072] In still another modification, the diffusing surface 3b of
the light guide plate 3 may be formed into a sawtooth shape. FIG. 9
is a sectional side view illustrating the light guide plate 3 of
the modification. In this modification, the diffusing surface 3b
includes triangular patterns 40 that are periodically arranged with
a predetermined pitch along the propagation direction of the
incident light incident from the incident surface 3a. Each pattern
40 includes a relatively wide first reflecting surface 41 and a
second reflecting surface 42 narrower than the first reflecting
surface 41. The first reflecting surface 41 is formed such that a
thickness of the light guide plate 3 increases with distance from
the first light source 4. The second reflecting surface 42 is
formed such that the thickness of the light guide plate 3 decreases
with distance from the first light source 4. For example, the first
reflecting surface 41 is formed at an angle of 10.degree. to
20.degree. with respect to the outgoing surface 3c so as to totally
reflect the light propagating through the light guide plate 3. On
the other hand, the second reflecting surface 42 is formed at an
angle (for example, 70.degree. to 80.degree.) larger than that of
the first reflecting surface 41 with respect to the outgoing
surface 3c such that the light, which is reflected by the first
reflecting surface 41 and incident on the second reflecting surface
42, is totally reflected and oriented toward the direction
substantially perpendicular to the outgoing surface 3c as indicated
by an arrow 901.
[0073] In still another modification, the light guide plate 3 may
be a front light type light guide plate.
[0074] In still another modification, as illustrated in FIG. 10, a
louver film 7 that blocks the obliquely incident light may be
arranged between the light guide plate 3 and the object 10. In this
case, the second light source 5 is arranged on the side of the
object 10 with respect to the louver film 7 so as not to be
affected by the louver film 7. The louver film 7 is an example of
the direction-selectivity light shielding member. In the louver
film 7, a plurality of plate-like opaque members 71 are arranged
with a predetermined pitch along the propagation direction of the
light emitted from the first light source 4 in a plate-like member
made of a transparent material such as transparent resin. For
example, the plurality of opaque members 71 are orthogonal to the
surface facing the light guide plate 3, and extended along the
direction intersecting the propagation direction of the light
emitted from the first light source 4. Particularly, the plurality
of opaque members 71 are desirably extended along a direction
substantially parallel to the direction in which the prism 11 is
extended. For example, the predetermined pitch may be set less than
or equal to the width from the end on the side facing the light
guide plate 3 of the opaque member 71 to the end on the side facing
the object 10. Therefore, even if the light from the first light
source 4 is output from the back surface side of the light guide
plate 3, the light is blocked by the opaque member 71, and the
object 10 is prevented from being illuminated with the light. On
the other hand, the opaque member 71 does not block the light
perpendicularly incident on a surface 72 of the louver film 7
facing the object 10. The light is emitted from the second light
source 5, reflected or scattered by the object 10, and
perpendicularly incident on a surface 72 of the louver film 7.
Then, the light can be transmitted through the light guide plate 3
and the liquid crystal panel 2 to reach the observer. Therefore,
the liquid crystal panel 2 is in the transparent state even if the
louver film 7 exists, and the observer can visually recognize the
object 10 while the second light source 5 is lit.
[0075] In this modification, desirably the light guide plate 3 is
formed such that, in the light leaking from the first light source
4 to the back surface side of the light guide plate 3, the amount
of light in which the angle formed with the normal of the diffusing
surface 3b of the light guide plate 3 is greater than or equal to
the viewing angle of the louver film 7 becomes at least double the
amount of light in which the angle formed with the normal of the
diffusing surface 3b of the light guide plate 3 is less than the
viewing angle of the louver film 7. Alternatively, desirably the
light guide plate 3 is formed such that, in the light leaking from
the first light source 4 to the back surface side of the light
guide plate 3, the amount of light in which the angle formed with
the normal of the diffusing surface 3b of the light guide plate 3
is greater than or equal to 45.degree. becomes at least double the
amount of light in which the angle formed with the normal of the
diffusing surface 3b of the light guide plate 3 is less than
45.degree..
[0076] In this modification, because the object behind the light
guide plate is constrained from being illuminated with the light
output onto the back surface side from the light guide plate 3, the
observer can further hardly visually recognize the object behind
the light guide plate while the first light source is lit.
[0077] In still another modification, a polarizer may be arranged
between the light guide plate 3 and the object 10 so as to transmit
only a polarization component having a polarization plane of a
predetermined direction. In this case, the second light source 4 is
arranged closer to the side of the object 10 with respect to the
polarizer. In this case, desirably the polarizer is arranged such
that a transmission axis of the polarizer is oriented toward the
same direction as a transmission axis of the polarizing plate on
the back surface side included in the liquid crystal panel 2.
[0078] In this modification, the light from the first light source
4 attenuates by being transmitted through the polarizer. When the
light is reflected or scattered by the object 10 to change the
polarization direction of the light, the light attenuates again by
being transmitted through the polarizer before being incident on
the light guide plate 3 again. On the other hand, the light that is
emitted from the second light source 5 and reflected or scattered
by the object 10 attenuates once by being transmitted through the
polarizer. Accordingly, in this modification, even if the light
from the first light source 4 is partially output onto the back
surface side of the light guide plate 3, the light from the first
light source 4 is attenuated more than the light from the second
light source 5 by the polarizer, so that the observer can further
hardly visually recognize the object behind the light guide plate
while the first light source is lit.
[0079] In still another modification, in order to prevent the
object 10 from being illuminated with the light from the first
light source 4 or environmental light, a light shielding member
made of an opaque material may be provided so as to surround the
object 10. In this case, for example, the light shielding member
can be formed into a hollow box shape in which a surface facing the
light guide plate 3 constitutes an opened end. For example,
desirably the object 10 is arranged so as to be located farther
away from the light guide plate 3 than the opened end of the light
shielding member. In this case, according to one or more
embodiments of the present invention, the second light source 5 is
also arranged in the light shielding member so as to be able to
illuminate the object 10.
[0080] In still another modification, desirably the object 10 and
the light guide plate 3 are arranged so as to separate from each
other by a predetermined distance such that the light emitted from
the first light source 4 is not incident on the light guide plate
3, or such that the light, which initially reaches the diffusing
surface 3b of the light guide plate 3 and is output onto the back
surface side from the diffusing surface 3b, is not incident on the
light guide plate 3 by the reflection of the light from the object
10. In this case, for example, the distance between the object 10
and the light guide plate 3 can be set greater than or equal to L
cos(.pi./4). Where L is a length of the light guide plate 3 from
the incident surface 3a to the side surface on the opposite side.
Therefore, even if the surface on the side facing the light guide
plate 3 of the object 10 constitutes the flat surface while being
parallel to the light guide plate 3, the light that is emitted from
the first light source 4 and mirror-reflected by the object 10 is
prevented from being incident on the light guide plate 3.
[0081] The display device of the embodiment and the modifications
may be mounted on game machines such as a pachinko game machine and
a reel type game machine.
[0082] FIG. 11 is a schematic perspective view illustrating a
pachinko game machine including the display device of the
embodiment and the modifications when the pachinko game machine is
viewed from a player side. As illustrated in FIG. 11, the pachinko
game machine 100 includes a game board 101 that is of a game
machine body provided in a most region from the top to a central
portion, a ball receiving unit 102 provided below the game board
101, an operation unit 103 provided with a handgrip, and a display
device 104 provided in the substantial center of the game board
101.
[0083] For the purpose of the game performance, the pachinko game
machine 100 includes a fixed accessory unit 105 provided in a lower
portion of the game board 101 in the front surface of the game
board 101 and a movable accessory unit 106 arranged between the
game board 101 and the fixed accessory unit 105. A rail 107 is
arranged in a lateral surface of the game board 101. Many obstacle
nails (not illustrated) and at least one winning device 108 are
provided on the game board 101.
[0084] In the operation unit 103, a game ball is launched with a
predetermined force from a launching device (not illustrated)
according to a turning amount of the handgrip operated by the
player. The launched game ball moves upward along the rail 107, and
drops among the many obstacle nails. When a sensor (not
illustrated) senses that the game ball enters one of the winning
devices 108, a main control circuit (not illustrated) provided in
the back surface of the game board 101 delivers a predetermined
number of game balls to the ball receiving unit 102 through a game
ball delivering device (not illustrated) according to the winning
device 108 that the game ball enters. The main control circuit
drives the display device 104 through a performance CPU (not
illustrated) provided in the back surface of the game board
101.
[0085] The display device 104 is an example of the display device
of the embodiment and the modifications, and attached to the game
board 101 such that the front surface side of the liquid crystal
panel is oriented toward the player. In response to the control
signal from the performance CPU, according to the game state, the
controller of the display device 104 puts the liquid crystal panel
into the transparent state such that the player can visually
recognize the object (not illustrated) arranged behind the display
device 104, or puts the liquid crystal panel in the opaque state
such that various images and graphics are displayed on the liquid
crystal panel.
[0086] Thus, those skilled in the art can make various changes to
the above embodiments without departing from the scope of the
present invention.
[0087] While the invention has been described with respect to a
limited number of embodiments, those skilled in the art, having
benefit of this disclosure, will appreciate that other embodiments
can be devised which do not depart from the scope of the invention
as disclosed herein. Accordingly, the scope of the invention should
be limited only by the attached claims.
* * * * *